The internal combustion engine has been around for over a hundred years. During this time there have been countless cases where the engines pumping function has been impaired. However diagnosing these air flow problems can be very difficult. There have been multiple ways designed to locate such problems. Early on the basic diagnostics included a vacuum gauge. By watching the vacuum within the engine was one way to diagnose such problems. However it is evident that this method had problems. Perhaps the biggest problem is in the speed that the engine is turning and the slow response produced from the mechanical vacuum gauge. Additionally there is no way in which to sync the vacuum gauge to the problem cylinder or cylinders.
More recent attempts to solve this problem would be shown in U.S. Pat. No. 6,484,589 by Brock. Brock discloses a piezo sensor for tracking fluid changes from a pump. Senx Technology makes Brocks sensor, “the first look sensor”. This is a piezo sensor that is used in the automotive industries. This sensor produces an electrical output that is based on a piezo differential sensor. This sensor responses quickly to changes in pressure but does not account for any amount of pressure or volume that is constant, just the changes within the pressure. The greater the pressure change the greater the voltage output form the piezo element. During a pressure change the sensor responses by producing a voltage output, however once the pressure change has occurred, and the pressure is at a constant (stable) pressure the sensors output will stop. The voltage output from this sensor has no scale that is proportional to the applied pressure. Additionally this sensor can produce ringing that is unwanted. This sensor would be used with a graphing multimeter, oscilloscope and can sync to the engine so the cylinder or cylinders in question could be identified.
Another method that can account for the volume and pressure changes within the internal combustion engine is accomplished with a pressure transducer as seen in U.S. Pat. No. 7,899,608 by Thompson. Since the pressure transducer produces an output that is proportional to the applied pressure the pressure can be accurately read. However the pressure transducer has limitations when used in the internal combustion engine. For example, if the engine does not have a throttle plate or the throttle plate is held wide open, and the engine has a slow rotation there is not enough volume change to change the pressure within the induction system of the engine. Therefore the changes produced from the pressure transducer are minimal. If the throttle plate is present and closed during low Revolutions Per Minute (RPM), it provides a restriction within the induction system that the cylinders can pull against. Therefore the volume in the intake manifold is displaced by each cylinder, thus creating larger pressure changes that produce a larger signal from the pressure transducer. In this condition each volume change can be accurately read by the pressure reading produced from the pressure transducer. The pressure transducer would be used with a, multimeter, graphing multimeter, or oscilloscope, and when used with a graphing multimeter, or oscilloscope can sync to the engine so the cylinder or cylinders in question could be identified.
In summarizing both sensors, the piezo and the pressure transducer have problems with producing a good signal when the engine does not have a throttle plate or the throttle plate is held wide open at crank, idle, and light loads. This is due to a low pressure differential within the induction system in these conditions.
What is needed is a way to accurately read the volume changes produced from the internal combustion engine like the pressure transducer accomplishes, while having the rapid changes occur like the differential piezo sensor accomplishes, without having the unwanted ringing. Additionally this needs to be accomplished where there is a throttle plate in the induction system, or where there is not a throttle plate within the induction system. The present invention accomplishes these goals.